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Home > Success Center > Log & Event Manager (LEM) > Log & Event Manager (LEM) Documentation > LEM fails to send rule notifications and emails

LEM fails to send rule notifications and emails

Updated: July 3, 2018


Over time, LEM may experience delays or failures in sending notifications for rules. Restarting resolves this issue, but over several hours or days, emails from rules will continue to fail.


  • All LEM versions



LEM sending queries to DNS servers that do not use query forwarding. This adds a resolve delay.


There are two methods to resolve this issue. One is configuring the DNS server, the second requires assistance with root access from SolarWinds Customer Support.

Contact SolarWinds Customer Support and ask them to verify DNS resolve times with the following command:


~ # dig @DNS-IP Test-Node-IP | grep "Query time"

;; Query time: 1161 msec

~ # dig @DNS-IP Test-Node-FQDN | grep "Query time"

;; Query time: 5 msec


Any results over 100ms will eventually lead to delays in rule processing. Ideally, the DNS should resolve in under 10ms.

Resolution 1

  • Configure query  forwarding on the DNS servers.

Requires the DNS team's assistance.

Resolution 2

Please contact SolarWinds Customer Support for assistance.

Increase queue size from 5k to 20k; increase parallel resolutions to 50; cache results for 2 hours instead of 15 minutes.

  • Create backup for manager.conf 
  • Edit manager.conf


  • IpLookupQueueSize=20000
  • CorrelationThreads=50
  • IpCacheTimeout=7200000
  • Save manager.conf
  • Verify user/group and permissions are correct for manager.conf
  • Restart LEM


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